A ductless mini-split is the right answer when a house has no ductwork to work with, or ducts that can't reasonably be extended to the rooms that need help. In Boone County that describes an unusual share of the housing: Sturgeon's median home was built in 1958 with 53.6% predating 1960, Rocheport's and Hartsburg's medians are both 1938, and Columbia itself contains 17,817 units built before 1980.
Which houses are we actually talking about?
| Community | Median year built | Age of the stock |
|---|---|---|
| Rocheport | 1938 | 58.0% built before 1940; 63.9% before 1950 |
| Hartsburg | 1938 | 52.7% built before 1940 |
| Sturgeon | 1958 | 53.6% before 1960; 74.7% before 1980 |
| Centralia | 1971 | 62.2% before 1980; 530 units predate 1940 |
| Columbia | 1993 | 17,817 units built before 1980 |
Columbia's own older neighborhoods — Historic Old Southwest, East Campus, North Central — sit inside that 17,817, and they raise the same retrofit questions as a farmhouse outside Sturgeon does.
Why don't these houses have ducts?
Because nothing about how they were built anticipated forced air. Balloon-framed houses of the 1880s–1930s were heated by stoves, radiators or a single gravity furnace pushing warm air up through one big central register. There are no chases in the walls, no soffits, and often no basement headroom to run a trunk line under.
Add ducts later and the cost isn't money alone — it's closet space, dropped ceilings and boxed corners in rooms with original trim. Where ducts were retrofitted decades ago, they're frequently undersized and high-static, which is why the back bedroom has never been comfortable in any season. A duct evaluation tells you which of those two situations you're in.
What is a mini-split, exactly?
An outdoor compressor unit connected to one or more indoor heads by a refrigerant line set. Each head serves its own zone with its own thermostat, and because it's a heat pump, each one both heats and cools. No trunk line, no plenum, no return grille the size of a door.
The zoning is the part homeowners notice most. In a house with a 1938 floor plan, the difference between one thermostat fighting six rooms and six rooms each holding their own setpoint is not a subtle upgrade.
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Where do mini-splits earn their keep?
- Houses with no ductwork at all — radiator, boiler or space-heated homes that have never had central cooling.
- Additions and sunrooms — the rooms the original system was never sized to reach.
- Enclosed porches and converted attics, where extending a duct means crossing an unconditioned space.
- Rooms over garages, which lose heat on three sides and always run behind the rest of the house.
- One chronically bad room in an otherwise fine system — often cheaper to solve directly than to rebalance the whole house.
- Upstairs bedrooms in a story-and-a-half, where the existing return simply cannot move enough air.
What does installation actually involve?
- A room-by-room load calculation. Old houses have wildly uneven loads — a south-facing room with original single-glazed windows behaves nothing like the room behind it.
- Head placement. High wall, floor console or ceiling cassette, chosen for the room and for where the line set can reasonably run.
- A small wall penetration for each head, carrying refrigerant lines, power and the condensate drain.
- The outdoor unit on a pad or wall bracket, kept clear of roof runoff and drifting snow.
- Commissioning — vacuum, charge verification, condensate testing and setting the controls for how the house is actually used.
- The permit. Inside Columbia, mechanical work is permitted through the city; unincorporated Boone County requires a permit too. Our permit guide explains who to call.
Compared with adding ductwork to a finished old house, this is a modest intervention — which is precisely why it suits places like Rocheport, where the historic district includes buildings dating from 1830.
Do ductless systems qualify for a rebate?
A ductless system is a heat pump, so for a City of Columbia Utilities electric customer the same replacement tiers apply when the AHRI Directory rating meets the 15.2 SEER2 minimum — $800 at 15.2–18.1 and $1,200 at 18.2 and above, on a replacement, with the application due within six months and the final mechanical permit in the packet. Ductless configurations vary a great deal, so confirm your specific system with Columbia Water & Light at Efficiency@CoMo.gov or 573-441-5528 before counting on it. Our claim walkthrough covers the paperwork.
Outside the city, Boone Electric's published HVAC rebates cover ground-source geothermal at $750 per ton and dual-fuel systems at $300, both expiring 12/31/2026 — so ask the co-op directly rather than assuming a ductless system qualifies. Boone Electric serves all of Rocheport and all of Harrisburg; other towns are served by other utilities. Check the name on your electric bill.
⚠️ No federal credit in 2026
The federal 25C and 25D tax credits both ended for property placed in service after December 31, 2025, under Public Law 119-21. If a ductless quote includes a federal credit for a 2026 install, it's quoting something that no longer exists. What changed →
What else should an old house get looked at for?
Comfort in a hundred-year-old house is rarely one problem. Air sealing and insulation usually matter more than equipment capacity; original windows move a lot of heat; and indoor air quality deserves attention in homes with stone foundations and crawl spaces. If there is existing ductwork, cleaning and sealing it often does more than a new machine would. And whatever you install, an annual service agreement keeps filters and coils in shape — mini-split filters need attention more often than people expect.
Frequently asked questions
Why do so many old Boone County houses have no ductwork?
They were not built for it. Houses from the balloon-framing era were heated by stoves, radiators or a single gravity furnace, so there are no duct chases in the walls. Rocheport's median home was built in 1938 and 58% of its housing predates 1940, which is exactly the vintage where adding conventional ducts means giving up closets and ceiling height.
Does a ductless mini-split heat as well as it cools?
Yes. A mini-split is a heat pump, so it both heats and cools. Columbia's normal January low is about 21°F, which is the point where any air-source heat pump needs a defined backup-heat strategy, so in an older house the mini-split is often paired with the existing furnace or with supplemental heat in the coldest rooms.
How many indoor heads do I need?
It depends on how the house is laid out rather than on square footage alone. Open floor plans can often be covered by one well-placed head, while a house chopped into small rooms by original plaster walls needs a head per zone. We size room by room, because an oversized head short-cycles and leaves the room humid.
Do ductless systems qualify for the Columbia rebate?
A ductless system is a heat pump, so the same Columbia Water and Light replacement tiers apply when the AHRI Directory rating meets the 15.2 SEER2 minimum and you are a City of Columbia Utilities electric customer. Because ductless configurations vary, confirm the specific system with the utility at Efficiency@CoMo.gov or 573-441-5528 before counting on it.
How disruptive is a mini-split installation?
Much less than adding ductwork. Each indoor head connects to the outdoor unit through a small penetration in the exterior wall carrying the refrigerant lines, the power and the condensate drain. There is no opening of wall cavities to run trunk lines and no soffit building, which is the main reason this approach suits finished older homes.
Can a mini-split heat and cool an addition or a sunroom?
That is one of the most common uses. Additions, enclosed porches, converted attics and rooms over garages are usually the spaces the original system never reached, and a single-head ductless system conditions them without touching the rest of the house.